1. Field of the Invention
The present invention relates to an apparatus and method for sequentially displaying multiple high resolution images in a single display and more particularly to an improved drive means for such a display apparatus.
2. Description of the Prior Art
A great demand has arisen for display advertising using animation and multiple advertisements at individual popular display locations thereby enabling a number of advertisers to benefit from a single location. Numerous different methods and devices have been proposed for preparing and displaying such advertisements. Many such devices involve relatively unwieldy mechanical elements driven by complex drive mechanisms which often generate noise at an annoying level. In addition to the expense of original manufacture, the user is often faced with expensive maintenance.
Typically, these devices are used in public retail outlets or other public locations. It is desirable to display multiple advertising images wherein the exchange from one image to another is nearly instantaneous thereby enabling the sequential display of different images in a manner where the exchange is imperceptible to the human eye from a distance of several feet and beyond from the display. Such a sequential display tends to draw and hold a viewer's attention without an annoying perception that one view is being broken up and another assembled.
Display devices have included transparency sheets having images thereon illuminated by back lighting through an overlay mask which blocks the back lighting from illuminating certain areas of the transparency sheets. Animated displays have included a grid having alternate opaque and transparent strips and a photographic transparency on which discrete images are arranged in parallel image strips which are moved relative to one another to give the impression of animation. The image strips of the photographic transparency are wider than the transparent strips of the grid. When the center lines of a set of image strips are aligned with the transparent lines of the grid, only three fifths of each strip is visible. Thus, some image information is lost. A device of this type is shown, for example, in U.S. Pat. No. 3,742,631 to Hasala. Because the image strips are only moved laterally, for a display of more than two images from one composite mosaic, the relative travel between the mask of transparent sheets must be considerable adding to the noise level and generating unwanted movement likely to distract the viewer.
Display devices have also included a grid moved in a square pattern over a transparent sheet to display a series of images selected from a composite of individual images. The transparent sheets are fully developed with several different appearances making up the visual display. A drive motor is utilized to drive a cam and cam follower to move the grid. The mechanical confrontation between the cam follower and the cam on the drive motor is loose and lacks precision. A device of this general type is shown in U.S. Pat. No. 4,306,226 to Swarbrick. Because of the lack of precision in relative movement, the apertures in the grid are made smaller than the pixels of the transparent sheet to account for errors in grid placement when the grid is shifted over the transparent sheet.
Devices have been proposed which include translucent image screens made up of mosaics of discrete images formed by interlaced translucent pixels which are arranged in uniform groups. Pixels corresponding to an image occupy the same relative position in each group. The image screen is covered with an opaque screen having a uniform pattern of transparent apertures. The opaque screen blocks back lighting from shining through the image screen except through the apertures. The uniformly patterned apertures are then aligned with pixels which correspond to an image and the image is thereby displayed by the back lighting shining through the image screen and the apertures. The opaque screen is selectively shifted on the image screen such that the apertures align with the pixels of a different image. A device of this general description is shown in U.S. Pat. No. 4,897,802 to Atkinson et al. Notwithstanding the excellent operational characteristics of the aforementioned patent, it is desirable to have a better drive system enabling precise and accurate registration between such an image screen and the opaque screen.